Factors Affecting Air Conditioning System:

In this modern age everybody is trying to improve his surroundings in order to make living conditions more comfortable. Air conditioning is one of the important contribution in this respect. The technique of maintaining of air condition inside a building in such a way that produces comfort to human beings, ensures trouble free operation of delicate equipment or helps in industrial manufacturing operations is called air conditioning. It involves control of temperature, cleanliness, humidity and circulation of air. The important factors affecting air conditioning system are :

1. Temperature Control: In air conditioning, temperature control means the maintenance of a particular desired temperature within an enclosed space even though the outside temperature may be either above or below the desired inside temperature. This requires either the addition or removal of heat from the enclosed space as and when necessary. For this purpose the outside air to be supplied in the room is either cooled or heated.

In summer, air is cooled by one of the following methods :

  1. Circulation of cold water.
  2. Evaporative system using water.
  3. Ice activated system.
  4. System using absorption principle.
  5. Vapour compression system employing a compressor, evaporator and a suitable refrigerant. This is commonly used method. Three arrangements are possible under it namely (a) individual window type or floor mounted package type air conditioners (b) a central plant employing chilled water in combination with unit conditioners located at various parts of the building and (c) a central plant with a ducting system to convey cooled air to the different parts of the building.

In winter, air is warmed by one of the following methods :

  1. Electric heaters
  2. Electromechanical heat pumps and
  3. Heat exchangers using waste system.

2. Humidity Control: Humidity control means the increasing or decreasing of water contents of air in order to create comfortable and healthy environments depending upon a particular season—summer or winter. Control of humidity is not only necessary for human comfort but also it increases the production and the efficiency of the workers. It has been found to improve the quality and to reduce the cost of the production of products like automobiles, clay products, drugs, chemicals, electric goods, foods, textiles etc. It is seen in factories during winter season or summer season, that though there is a normal environmental temperature yet the workers feel uneasy. That is due to lack of proper water contents or humidity of air. The humidity control is achieved by the process of humidification (addition of humidity or moisture) or dehumidification (reduction of humidity or water vapour). The humidification is accomplished either by supplying or spraying steam or hot water or cold water into the air. Dehumidification may be accomplished by using an air washer or by using absorbents. In the air washer system, the outside air is cooled below dew point temperature so that it loses moisture by condensation. The moisture removal is also accomplished when the spray water is chilled water and its temperature is lower than the dew point of the outside air. The absorbent materials are activated alumina, silicagel and calcium chloride. These are generally used for window type small room coolers. In general, for summer air conditioning, the relative humidity should not be less than 60% while for winter air conditioning it should not exceed 40%.

3. Air-movement and Circulation: In order to keep constant temperature throughout the conditioned rooms, it is necessary that there should be equi-distribution of air throughout the space to be air conditioned. For this purpose the air movement and its circulation should be controlled.

4. Air-filtration, Cleaning and Purification: Proper filtration, cleaning and purification of air is necessary to keep it free from dust, dirt and other impurities which are very injurious to health. The dust particles are liable to clog the nose, throat and lungs of the worker seriously affecting their health. The dirt present in air acts as a carrier of germs and is responsible for disease spreading. In case of certain industries like chemicals the dirt produced as a byproduct is very harmful for health if inhaled. The presence of dirt in the air used for air cooling of electrical machines and diesel sets in power plants is liable to clog their air passage resulting in reduced efficiency and life. Various types of air impurities other than gas or vapours called the Aerosols are also present. These are dust (earthly wet soil dust, dust of coal, cement, wheat, lint a string like dust from cotton or wool); fumes (solid particles  due to condensation and solidification of gaseous substances, zinc oxide fumes from zinc vapours); smoke (due to combustion of organic materials like tobacco, wood, oil, coal etc.); pollen (from weed, tree, flower and other vegetation – may be harmless of harmful); bacterial (living micro-organisms) etc.

There are various methods of cleaning, filtering and purifying the air from the above mentioned impurities. Mists or fogs in the air are usually removed by raising the temperature of air. This results in the formation of small suspended water particles into vapours making them invisible. The impurities like gases and vapours are removed by the process of condensation. Pollen grains responsible for hay fever, rose fever and other respiratory difficulties are removed by filters or by using a wet space. The particle of pollen grains will adhere to these wetted surfaces.

Bacteria present in the air is removed either by filter chemicals or by using a sterilising light of ultraviolet rays. For proper air sterilisation special ultraviolet ray lamps of radiation 2,600 Angstrom units are used. These are generally placed near the outlet grille on its inside end. They are shielded properly to avoid exposure of skin or eyes. Ultraviolet lamps are largely used in meat packing houses and storage rooms to avoid the growth of bacteria. Fine powder of propylene or triethylene glycol is also sprayed in the air to kill bacteria.

To remove dust particles from the air four methods using equipment’s like centrifugal devices, water filters or air washers, adhesive impregnated filters, electrostatic precipitators are used.

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